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8
BASIC RADAR THEORY
■ Multiple echoes
Multiple echoes may appear when a short-range
and strong echo is received from a vessel, bridge, or
breakwater.
Your vessel
Another vessel
Multiple echoes will appear beyond the target’s true
echo point on the same bearing of a large target. They
can be reduced with proper adjustment of the [SEA]/
[ ] control.
See page 18 for the [SEA]/[ ] control.
■ Minimum range
Detection at short range is very important. Minimum
range is determined primarily by transmitter pulse
length, vertical beam width and height of the scanner
unit. The shorter the transmission time, the quicker the
return echoes can be received and their distance mea-
sured.
The ability to see targets very close to the vessel is
decreased if the scanner is mounted too high off the
water, because the bottom of the vertical beam of the
scanner overshoots nearby targets.
This target cannot be detected by radar.
The target in this area cannot be detected.
Pulse length
Pulse starting point
Vertical beam width
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